WASHINGTON, D.C. -- The blunder by federal prosecutors that brought the Roger Clemens trial to an unexpected end could kill the entire prosecution and free Clemens to try to reclaim his legacy.

Moments after he declared a mistrial on Thursday, U.S. District Judge Reggie Walton wondered aloud to the packed courtroom, "Now we must address whether the defendant [Clemens] can be re-prosecuted."

Former Major League Baseball pitcher Roger Clemens, center, with his attorneys Michael Attanasio, left, and Rusty Hardin leaves federal court Thursday in Washington after his perjury trial ended in a mistrial. AP Photo/Alex Brandon

The legal doctrine that prompted the judge's query is known as "double jeopardy," and it could result in Walton's telling the prosecutors that they will have no second chance to prosecute Clemens on charges of obstruction of Congress and perjury.

The ban on "double jeopardy" comes from the U.S. Constitution, and it means that prosecutors have one chance to convict someone accused of a crime. If the accused individual is found not guilty, there can be no do-over for the prosecutors.

The accused can be put in jeopardy of punishment only once. There can be no second trial and no "double jeopardy."

Lawyers, judges and law professors can argue endlessly about the constitutional ban on double jeopardy. If six of them discussed and analyzed the issue, there would be six conflicting opinions.

The arguments begin with the question: At what point in a trial does double jeopardy become an issue? How far along must the trial proceed before it qualifies as the prosecutors' one and only chance to obtain a conviction?

Most experts agree that "jeopardy attaches" -- the legal phrasing -- when the jurors are selected and sworn in to decide the case. There is little doubt that jeopardy has attached in the Clemens trial, but other issues will determine whether Walton gives the prosecutors a second chance.

One of the principal issues in that decision will be his determination of whether the blunder was inadvertent or deliberate or somewhere in between.

Quietly seething as he deliberated the mistrial decision, Walton said: "Government counsel [should] not do whatever they can get away with doing." It was a clear signal that he might conclude that prosecutors Steven Durham and Daniel Butler might have deliberately tried to bring before the jury evidence that Walton had barred in a pretrial ruling.

His pretrial ruling was that the prosecutors would not be permitted to use Andy Pettitte's wife, Laura, as a witness to confirm Andy's account of Clemens' admission that he used human growth hormone. Andy testified that he told Laura about Clemens' admission shortly after their conversation. Walton ruled on July 7 that a statement from Laura violated federal hearsay rules.

But despite Walton's decision barring mention of Laura as confirming witness, the prosecutors played a video excerpt from Clemens' testimony at the House committee hearing on Feb. 13, 2008, that included Rep. Elijah Cummings' (D.-Md.) description of Laura confirming Andy's account of Clemens' alleged admission.

The prosecutors' violation of the court order was sufficiently egregious for Walton to halt the video even before Clemens' attorney Rusty Hardin objected.

Calling the prosecutors and Hardin to a conference out of earshot of the jury, Walton described the problem in increasingly angry terms. At one point, explaining that it was the responsibility of the prosecutors to remove references to Laura from the video, the judge stated with disgust that "any first-year law student would have known to do that."

Hardin, shrewdly biding his time as the judge continued to describe the problem, waited for exactly the right moment to ask for a mistrial. His request came only after Walton's statements and observations had made the mistrial inevitable.

If Walton, as he indicated in his statements in court, continues to view the prosecution error as deliberate, there might not be a second trial.

In addition to the possibility that it was a deliberate violation of the order, the mistake came with reference to a witness, Andy Pettitte, whom Walton regards as "the most critical" in the case.

"They [the Clemens lawyers] can attack [former personal trainer] Brian McNamee all day, but it will be difficult for them to undermine Pettitte's credibility," Walton said.

Clemens, in his testimony before the House committee, agreed with Cummings that Pettitte was one of the "most honest people in baseball."

With Clemens already agreeing to Pettitte's veracity, Walton explained, it was "highly inappropriate" to mention Laura's corroboration of Andy's account of Clemens' admission.

If the violation of a pretrial order had come with any of the 44 other government witnesses, there would have been no mistrial.

Walton's conclusion that the government prosecutors were guilty of a "direct violation of my ruling" adds to the likelihood that he will rule against a second trial.

The prosecutors' best chance to preserve their opportunity for a second trial will be to present a convincing argument that their work on the trial evidence was careful and professional and that there was no deliberate intent to violate Walton's order.

The prosecutors will try to explain what happened in a brief that they must file with Walton by Aug. 19. If there is to be a second trial, the brief and its supporting documents must show a good-faith effort to prepare a huge quantity of evidence in a complex case.

Their best chance for a second trial will be an assertion, supported by sworn affidavits from staff members, that they were overwhelmed and understaffed, which led to an innocent mistake.

It will be a tough sell. The prosecutors had been doing so well that it seems implausible that they would have made a mistake on Laura Pettitte.

Prosecutor Durham had done a masterful job in his opening statement and was building powerful evidence on the difficult issue of the committee's authority to investigate baseball when the video blunder occurred. The prosecutors' work throughout the process has been high-quality and nearly error-free.

A mistrial like this is a rare event in federal courts. Deliberate defiance of a judge's order by federal prosecutors is even rarer. If this combination of rare events has indeed occurred, it could allow Clemens to walk away from a massive investigation and prosecution that seemed likely to send him to prison.

Lester Munson, a Chicago lawyer and journalist who reports on investigative and legal issues in the sports industry, is a senior writer for ESPN.com.